1. Field of the Invention
The invention relates generally to a method of manufacturing a capacitor in a semiconductor device. More particularly, it relates to a method of manufacturing a capacitor in a semiconductor device capable of improving the leak current characteristic while preventing degradation of a dielectric characteristic of a Ta2O5 capacitor.
2. Description of the Prior Art
Generally, the Ta2O5 capacitor is manufactured in a MIS (Metal-Insulator-Silicon) structure in which a TiN film/polysilicon film structure is stacked as an upper electrode. The reason why the stacked TiN film/polysilicon film is used, is that it can improve the leak current characteristic of the TiN film since it has the value of a higher work function compared with the polysilicon film.
However, there are the following problems when using the TiN film as the upper electrode. That is, the process of forming a CVD TiN film using a mixed gas of TiCl4+NH3 will increase the leak current in the Ta2O5 dielectric film due to a halogen gas. Also, there will happen an interface reaction between the Ta2O5 dielectric film and the TiN film at the temperature of about 500xc2x0 C., thus causing oxygen within the Ta2O5 dielectric film to flow into the TiN film. Thus, oxygen vacancy will be created within the Ta2O5 dielectric film, resulting in increase of the leak current. The reaction between the Ta2O5 dielectric film and the TiN film can be expressed into the following chemical equation. The TiO2 film formed by this chemical reaction will degrade the capacitor characteristic of the TiO2 film.
5TiN+2Ta2O5xe2x86x92TiO2+4TaN+1/2N2 xe2x80x83xe2x80x83[Equation 1]
It is therefore an object of the present invention to provide a method of manufacturing a capacitor in a semiconductor device by which TaN is used as an upper electrode, which can improve the leak current characteristic of a Ta2O5 capacitor due to the high work function of a TaN while preventing degradation of the dielectric characteristic of the Ta2O5 capacitor, in order to prevent degradation of the dielectric characteristic due to the interface reaction between a Ta2O5 dielectric film and a TiN upper electrode in the Ta2O5 capacitor.
In order to accomplish the above object, a method of manufacturing a capacitor in a semiconductor device according to the present invention is characterized in that it comprises the steps of forming a lower electrode on a semiconductor substrate in which various components for forming a semiconductor device are formed, forming a Ta2O5 dielectric film on said lower electrode; and forming an upper electrode made of a TaN film on said Ta2O5 dielectric film.